https://bugs.gentoo.org/695954

--- a/mmm.texinfo
+++ b/mmm.texinfo
@@ -1,5 +1,6 @@
 \input texinfo
 @c %**start of header
+@documentencoding ISO-8859-1
 @setfilename mmm.info
 @settitle MMM Mode Manual
 @c %**end of header